I think the temps sound a bit warm to me. I usually don't let my warm side get over 86 and my cool side at most is 75...during the day. I wouldn't want my water to be that warm either...so that if the snakes got really warm, they could cool off in the water. At night, I keep the warm side around 70-75...and the cool side below 70...except with my babies, I let them stay warmer at night.

Oh...and yes, definitely use a thermostat...I would be worried all the time about my temps if I didn't have thermostats.